package com.demo8;

/**
 * Created by Administrator on 2017/3/27.
 */
public class YiChang4 {
    public static void main(String[] args) {
        method1();
    }

    static void method1() {
        method2();
    }

    static void method2() {
        method3();
    }

    static void method3() {
        String str = null;
        int n = str.length();
    }
}
